Engine



Feb. 25, 1930.

' c-r. R. LAWRENCE 1,748,072

ENGINE Filed Jan. 23, 1928 I 5 Sheets-Sheet l IN V EN TOR.

Feb. 25, 1930. LAWRENCE 1,748,072

ENGINE Fild Jan. 23, 1928 s Sheets-Sheet 2 IN VEN TOR. fiaazy Zwflwza Feb; 25, 1930. LAWRENCE 1,748,072

ENGINE Filed Jan. 23. l928- 3 Sheets-Sheet 5 Patented Feb. 25, 1930 GEORGE It. LAWRENCE, or CHICAGO, ILLINoIs' ENGINE Application filed arm 23, 1928. Serial No. 248,837.

1 This invention relates to improvementsin internal combustion engines, more particularly to two stroke cycle, scavenging gas engines for high speeds. 'The'main objects of i this invention are to provide a two stroke'cycle gas engine capable of such piston speeds as four to six hundred feet per minute in I order to obtain extreme lightness and high efiiciency; to provide means for supplying a '10, measured amount offuel to each cylinder; to

provide-for an even and steady distribution of the fuel to the several cylinders;and to provide a simple and reliable fuel supply mechanism which is capable of being operated at highrates of speed. 7 I

In the accompanying drawings l is illustrateda gas engineembodying my invention, in whichz Y v I Fig. 1 is a fragmentary side elevation of the upper portion of the engine, showing the fuel supply mechanism for a four cylinder, two

cycle, scavenging engine, having approximately a two and three-eighths inch bore and a three and three-quarter inchstroke. I ;-Fig'.2 is aplan view of'theparts shown in Fig. 1, with partsbroken'away and parts shown in section. V i Fig. 3'is a transverse section taken on line 3'3 ofFig. 1. p p r Fig.4is taken on line 44of Fig. 2.

5 Fig. 5 is taken substantially on line 5-5 of Fig. 2.

1 F ig. 6 isa section of the lower portion of the mixer,'taken on line 66 of Fig. 2. Fig. 7 isatiming diagram.

The engine shown in the drawings operates on the two cycle, scavenging principle, and asubstantially pure fuel vapor is injected into the cylinders instead of liquid 40 fuel. In other scavenging engines used heretofore a measured amount of air was blown through thecylinder as the cylinder wall exhaust. ports were uncovered; then a measured amount of mixture was blown in before the 4 ports were closed. j To obtain any but extremely slow speedsthe amount of'scavenging air-was necessarily limited because the i scavenging air and the mixture had to. both be'blown in during the period the exhaust ports were open. Usually the scavenging air volume of the cylinder. .dicates that the burnt charge was merely diless angularity was measured to be approximately 70% of the This, of course, in-

luted instead of completely cleaned out.

Such engines have been built in very large sizes, and have a long connection from the fuel and air pumps to the cylinders. Other engines such as the Diesel type oil burning engines injected the oil into the cylinders at the beginningofthe power. stroke with a pressure of about one thousand pounds on the oil 1 l and with a compression of between four and five hundred pounds in the cylinder, to obtain a slow burning, some of the burnt charge being purposely left in the cylinder to deaden the combustion.

Inthe present engine, several cylinder volumes of airare blown straight through the cylinder from the top, out through the exhaustports to thoroughly clean and also to cool the cylinder. Then a measured amount; of the-ifuel vapor is forced into the cylinder during the first half of the vcompression stroke. This allows more time for both the scavengingand the fuel injection; that is, these operations take place in a larger angle of crank shaft rotation. Accordingly, since .thefuel requires an appreciable amount of time to flow through the passages, the pistons may be operated at higher speeds than where is provided, and higher effi-;- ciencies obtained.

By more thoroughly cooling the inside of the cylinders and the piston heads, the danger of flare-backs is eliminated, and air cooling 35 throughout becomes feasible. Byinjecting the fuel during the first part of the compression stroke, only a low pressure is required onthe fuel. This decreases the amount of power used for handling the fuel, and permits lighter pumping mechanism. Also, in the, present invention, the pumps are very close to the cylinders. This shortens the passages and also increases the efliciency of the pumps and greatly reduces their size.

Another distinguishing characteristic of this invention is the manner in which one present invention, the cylinders are arranged to fire in a one-three-two-four, or a one-fourdriven from a shaft rotated at twice the num- "ber of revolutions of the engine crank shaft, and serve first one cylinder and then the other.

Each pump has two outlet connections, one to each cylinder of the corresponding pair, and each connection has a return check valve therein. As a result, the explosion pressure closes the check valve for that cylinder and the expulsion stroke of the fuel pump opens the other check valve and forces the fuel into the cylinder which is undergoing compres sion. v I I Referring to the drawlngs, the reservoir 1 and the fuelpuinps 2 are mounted at one side of the engine cylinders 3. Each pump is connected by a suction tube line) the reservoir- 1, and is provided with a piston 5,-connected to the double-time shaft 6. The shaft "6' is rotatably mounted in brackets 7, bolted I to the side of the hollow cam shaft-housing or engine head 8, and is geared in a two to one speed ratio to the cam shaft 9, which, in a two cycle engine, rotates at crank shaft speed.

The time shaft 9 is connected for driving to the engine crank shaft, not shown, to the crank pins of which the pistons 10 are connected by means of the connecting rods 11, in

such manner that the shaft 9 rotates in synchronism with the crank shaft. The upper ends of the cylinders 3 are each connected into the head 8 by flanged rings 12 which thread into the upper ends of the cylinders with the flanges gripping the upper surface of the plate 13 which is bolted to the bottom of the head 8, forming a closed air 1 space in the head. One largeair valve l lis provided in the upper end of each cylinder, seated on the end of the ring 12 and having the stem 15 slidably mounted in the bearing 16 which is formed in the bridge 17 across the ring 12. The valve spring18 seats against the bridge 17 and bears against the spring cup 19, which is attached to the upper portion of the valve stem.

A finger 20, pivotally mounted in the side wall of the head 8, is inserted between the upper end of the valve stem 15 and the valve operating cam 21 which is an integral part of the shaft 9. In the position shown. in Fig. 3 the piston is just starting the down-stroke,

or expansion stroke, the gas having been compressed on the up-stroke of the piston and fired by a spark plug 22, mounted in the spark plug boss 122. The spark plug may be of any form commonly used, and is fired by any suitable ignition device. The cam shaft 9 is rotating clockwise, and it will be seen that the air valve 14 has been closed during I the up-stroke of. the piston. Near the bottom of the'stroke, the piston uncovers the open exhaust ports 23, allowing the burnt gas to escape, and the air valve 14 is opened by the cam 21, as indicated in dotted lines in Fig. 3.

Air under pressure is supplied to the chamher in the head 8 in any suitable manner, as by an air compressor driven by the engine, so thatseveral volumes of air are blown through the cylinder before the piston again closes the exhaust ports23 on the return stroke. A v 7 measured amount of dense fuel vapor is then i forced into the clean air in thecylinder during the earlier part of the compression stroke to form an explosive mixture, and the new charge is then compressed and fired.

. A light, spring pressed return check valve 24; is provided in the bottom of the casing 25' of each fuel pump 2,, in theopening into the suction pipe 4, see Fig.v ,4. The outlet from the pump is through ahorizontal passage 26,in the bottom of the pump, see Figs. 2 and 4, which connects into a vertical passage 27, in the side wall of the casing 25, through a port 28, which is closed by a ball check valve 29, under pressure of a spring 127. A short distance above the ball check 29, the'passage 27 is connected into the two vertical passages 30.3O through short inclined passages 31, shown in dotted lines in Fig. 1. A ball check 32 is provided in each of the passages 30, and

the passages communicate through the nip ders,.above the highest position of the piston head.

cylinder.

WVhen one'pistonisnear the top center and the cylinder is under compression or under Thus it will be seen that the pump outlet connects into two oppositely functioned; cylinderswith a return check valve foreach ples 33 and tubes 34 into the adjacent cylinthe combustion pressure, thecorresponding check valve 32 in the connectionto the fuel pump is closed. Then, when the pump piston moves down and builds up sufiicient pressure the check valve 32 for the opposite cylinder is lifted and the fuel is forced into the proper cylinder.

The fuel 'vapor reservoir is common'to bothi fuel pumps, and comprisesja'shell 35 which is clamped between the upper and lower heads 36 and 37 by means of the central perforated pipe '38, which threads into the 7 lower head 37, and into thecap nut 39. The bottom head is provided with passages 40 connecting the pipes 4: to the interior of the center pipe 38; drain passages 41,.leadingx from the bottom of the chamber in the shell l small passages 42, the sudden expansion into rywraovg;

I 35 and inlet passages 42 leading to the supply pipe 43 which is connected into the lower head 37.

During the up-stroke of the fuel pump pistons 5, the check valves 29 and 32 in theoutlet passages are closed, and the check valve 24 islifted and a partial vacuum is set up in the passages leading to the reservoir, in the reservoir itself, and in the suction pipe 43 which leads from the reservoir down into the liquid in the liquid fuel receptacle 44.

The receptacle 44 is open to the atmosphere,

; and the supply of fuel liquid is maintained I is generated to fill the vacuum created by the pump. The bottom of the supply pipe 43 is substantially sealed to the air bythe liquid;

' and the vaporization of the fuel under the depressionscreated by'the quick jerks of the pumps, which operate at high speeds, is pro moted and sustained by the flow through the the chamber of the reservoir 1, and the action in flowing into the perforations in the pipe 38.

An appreciable amount of air is contained in all liquids, and especially in the highly volatile and unstable liquids used for fuel full period of the opening of theexhaust in internal combustion engines of the present type; and this contained air assistsmaterially in maintaining the fuel in the vaporized condition until it is pumped into the power cylinders of'the engine.

In this manner the volume of the small quantity of the fuel in its liquid state, which is required in each charge, and which is difficult to handle and measure, is increased by changing the fuel into a dense vapor. Then the volume is great enough to be conveniently handled by the available mechanical means,

" such as the relatively small piston pumps reservoir head 37, leading from the bottom of the reservoir chambersinto the passage 40 'to drain any surplus liquid out of the chamher, which is disposed of through the pumps.

The single reservoir assures an even supply of fuel to each pump, and the pumps are constructed to deliver a measured amount of the mixture to each cylinder. Control may be accomplished in any suitable manner, as by varying the strength of the mixture or by other methods which will be obvious to those skilled in this art.

The method of operation is best illustrated by the diagram shown in Fig. 7, which gives the complete cycle of operations by the angular positions of the crank shaft. The point a representsthe top center; theline b, approximately fifty degrees ahead of the bottom center, the point at which the piston'starts to uncover the exhaust ports; the'line c, the opening of the air valve; the line 6, the starting of the'down-stroke of the fuel pump; cl, the closure of the air valve and exhaust ports; and f,- at ninety degrees from e-the completion of the pump stroke. Since a certain amount of pressure is required in the pump to open thecheck valve 29 against the weight of the spring 127, the pump is effective for forcing fuel into'the cylinder under compression during only a portion of its stroke, as between the angular engine crank shaft positions 9 and h. The circle m represents the atmospheric pressure; p the combustion and expansion pressure; .9, the pressure head on the. scavenging air; and n, the compression pressures. The air valve is opened about ten degrees after the exhaust to take'advantage of thevelocity head of the gases flowing out of the exhaust ports, as well asfor lowering the pressures of the gases below the pressure on the air. The air valve may be closed with the exhaust or a few degrees ahead, and sufficient pressure is supplied to-the scavenging air to blow several cylinder volumes of air down through the cylinder.

It is now manifest that substantially the valves isjavailable for the flow of the scavenging air, which is of great advantage in. obtaining high speed; Considerable time is also allowed for injecting the fuel, and the in ection occurs during the beginning of the compression stroke before the higher pressures are reached, which reduced the amount of power required for injection, and also causes a more thorough mixing before the fuel is ignited. This also reduces the tendency of the pumps to leak, since the pumps only act against a low resistance.

Having thus described my invention my claims are as follows:

1. In an internal combustion engine, a plurality of cylinders, a vapor reservoir, means forgenerating a dense fuel vapor in the pumps connected to said reservoir, said pumps being separately connected to the different cylinders.

2. In an internal combustion engine, 2. cylin'der having a piston reciprocating therein, means for opening the cylinder near the end of the expansion stroke, means for blowing several volumes'of air through the cylinder while open, means for closing the cylinder at the beginning of the return stroke, a reservoir, means for generating a dense fuel vapor in the reservoir, a relatively small piston pump connected between the reservoir and the cylinder, and means for operating the pump to inject a measured amount of reservoir, a plurality of relatively small fuel the vapor into thecvlinder at about the time the cylinder is closed. Y I

3. In aninternal combustionengine, 2; cylinder having a piston reciprocating therein,

' means-for opening the cylinder near the end of the expansion stroke, means for blowing several volumes'of air through the cylinder while the cylinder is open, means for closing the cylinder during the return strokeof the piston, a reservoir, means for generating a v dense fuel vaporin the reservoir, and means for pumping the vapor from the reservoir intothe cylinder-in measured quantities at about the time the cylinder is closed;

4. In an internal combustion engine, a closed reservoir, a liquid fuel receptacle, an intake pipe connected into the reservoir and having its lower end immersed in the liquid in the receptacle, and a piston pump for creating a vacuum in the chamber and dis- 7 charging intoone of the cylinders of the engine at the proper time tosupply a measured quantity of the dense fuel vapor generated in the chamber by the depression into the engine cylinder. Y g

' I 5. In anvinternal combustion engine, a reservoir having a downwardly extending intake pipe, a liquid fuel receptacle, the lower end of the intake pipe being connected to the receptacle so as to communicate a vacuum to the liquid, means: for creating a vacuum in the reservoir, and means fortransferring the dense fuel vapor generated in the reservoir into the engine'cylinders.

GEORGE R. LAWRENCE. 

